Enantioselectivity and<i>cis</i>/<i>trans</i>-Selectivity in Dirhodium(II)-Catalyzed addition of diazoacetates to olefins
作者:Paul Müller、Corine Baud、Doïna Ené、Sharokh Motallebi、Michael P. Doyle、Bridget D. Brandes、Alexey B. Dyatkin、Marjorie M. See
DOI:10.1002/hlca.19950780217
日期:1995.3.22
comparable. Additions catalyzed by 1 are strongly sensitive to steric effects. Highly substituted olefins afford cyclopropanes in only poor yield. The preferential cis-selectivity observed in reactions catalyzed by 1 is attributed to dominant interactions between the ligand of the catalyst and the substituents of both olefin and diazoacetate, which overrule the steric interactions between olefin and diazoacetate
用[Rh 2 (4 S)-phox} 4 ](1 ; phox =四[[4 S)-四氢-4-苯基恶唑-2-酮])研究了Rh 11催化的重氮乙酸类酯类化合物向烯烃的加成反应。,[Rh 2 ((2 S)-mepy} 4 ](2 ; mepy =四[甲基(2 S)-四氢-5-氧杂吡咯-2-羧酸酯])和[Rh 2(OAc)4 ](3)。当用2和3催化时,优先提供反式-环丙烷羧酸酯,顺式-异构体是1的主要产品。通常,用1和2获得的对映选择性是可比较的。1催化的加成对位阻效应非常敏感。高度取代的烯烃仅以较差的收率提供环丙烷。在1催化的反应中观察到的优先顺式选择性归因于催化剂的配体与烯烃和重氮乙酸酯的取代基之间的显性相互作用,该相互作用抵消了烯烃和重氮乙酸酯在过渡态下的卡宾转移的空间相互作用。